US4624993A - Method for depolymerizing polymers - Google Patents
Method for depolymerizing polymers Download PDFInfo
- Publication number
- US4624993A US4624993A US06/699,658 US69965885A US4624993A US 4624993 A US4624993 A US 4624993A US 69965885 A US69965885 A US 69965885A US 4624993 A US4624993 A US 4624993A
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- polymer
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
- C08F8/50—Partial depolymerisation
Definitions
- This invention relates to a method for degrading or depolymerizing non-thermosetting, i.e., meltable, organic polymers. More particularly, the method comprises the thermal oxidative degradation of molten polymers by sparging them with small, oxygen-containing, gas bubbles of a particular size in the absence of a catalyst. The method is particularly useful for the treatment of amorphous polypropylene, homopolymers and copolymers of olefins, and synthetic waxes prepared by the Fischer-Tropsch process.
- organic polymeric chemicals provide an exceptionally complicated variety of chemical and stereochemical configurations.
- the chemical literature is replete with references concerning the production of such polymers and their treatment in order to alter their diverse physical and chemical properties for various industrial purposes.
- the polymerization reaction of simple alkene and conjugated dienes produces many useful substances of commerce.
- Numerous examples of polymerization exist, such as, the treatment of ethylene in the presence of oxygen, heat, pressure and catalysts to produce polyethylene, the polymerization of vinyl chloride to polyvinyl chloride, etc.
- Some of these polymerizations can be designed to produce stereospecific polymers.
- Polypropylene for example, can exist in a high melting crystalline form, a soft and rubbery amorphous form, and in various forms intermediate between these extremes.
- paraffin wax starting material can be produced from natural sources (petroleum or lignite) or can be produced synthetically (Fischer-Tropsch process).
- the oxidation of these waxes either by means of chemicals or through the use of air or other oxygen-containing atmospheres results in the formation of water-soluble fatty acids which have been used for the manufacture of soaps and various fatty acid esters.
- the oxidations also commonly produce undesirable degradation by-products having dark colors and/or unpleasant smells.
- an object of this invention is to provide a new, useful, simple, and inexpensive method for the thermal oxidative decomposition or depolymerization of polymers.
- a further, more particular, object of the invention is to provide a method for decreasing the viscosity and softening point or amorphous polypropylene.
- Yet another object is to provide a method for the oxidative decomposition of polyolefins, alpha-olefins, Fischer-Tropsch waxes, and mixtures thereof.
- An additional object is to provide a method for the oxidative decomposition of polymers which operates at low temperatures, does not use a catalyst, and has a fast reaction rate.
- organic polymers can be depolymerized rapidly at low temperatures without the aid of a catalyst by carefully regulating the flow rate and bubble size of an oxygen-containing atmosphere which is sparged through the polymer while the polymer is in its molten state.
- the method of the invention comprises reacting molten polymers at atmospheric pressure in the absence of catalysts at a temperature between about 270° F. (130° C.) and about 415° F. (215° C.) while sparging the molten material with an oxygen-containing gas at a flow rate of at least 2 cubic feet per minute (c.f.m.) per 1000 pounds of reactor charge, and preferably between 2 and about 20 c.f.m./1000 lbs. of reactor charge, where the gas bubble size (diameter) is less than about 10.0 mm, and is preferably between about 0.5 mm and about 5.0 mm.
- the molten material is constantly stirred as it is sparged. It is preferred to use air as the oxygen-containing gas, but pure oxygen gas or mixtures of oxygen and inert gases (e.g., nitrogen) can be substituted for air, if desired.
- the particular temperature at which the reaction is run depends upon the material being depolymerized and the desired end-product. In all cases, the temperature must be higher than the melting point of the starting material. Preferably, to avoid the production of undesirable by-products, the reaction is run at between about 25° F. and 50° F. above the melting point of the starting material. For example, reaction temperatures around 395° F. (385°-405° F.) have been found to result in successful depolymerizations of amorphous polypropylene having a melting point around 360° F., while for alpha-olefins and Fischer-Tropsch waxes, which melt in the range of 175° F. to 225° F., reaction temperatures on the order of 200° F. to 275° F. are used. Similar temperature ranges can be readily determined for other polymers by persons skilled in the art.
- reaction It is convenient to monitor the reaction by periodically removing samples from the reaction vessel and assaying them for softening point, viscosity, acid number, saponification number or a similar parameter.
- the reaction is stopped most conveniently by removing the material from the reaction vessel while continuing to sparge the material so as to prevent the molten polymer from backing up into the sparging apparatus.
- an oxidation inhibitor e.g., IRGANOX 1010 (Geigy Chemical Corporation, Ardsley, N.Y. 10502) BHT, or the like, to the finished product to prevent further degradation during storage and use.
- the present invention uses lower temperatures, shorter reaction times, and completely avoids the use of costly catalysts which required removal or deactivation in the prior art techniques. Indeed, catalysts cannot be used in connection with the present invention since they result in uncontrollably high reaction rates. In view of the reduced reaction time and the removal of catalyst, the present method is less costly than conventional methods. Moreover, the products produced by the method of the present invention have superior properties, e.g., better color and odor, than products produced by prior art techniques.
- the present invention relates to a method for depolymerizing polymers without the use of catalysts by melting the polymer and then sparging the molten material at a carefully controlled rate with an oxygen-containing gas which has been broken up into bubbles of a carefully controlled size.
- high molecular weight polymers including polyolefins (polymers of ethylene, propylene and higher olefins) are converted to lower molecular weight compounds by oxidation with air.
- Materials which can be depolymerized include: alpha-olefin, fully refined paraffin (F.R.P.), petrolatum, amorphous polymers and co-polymers, such as, amorphous polypropylene, amorphous polyethylene, amorphous ethylene-vinyl acetate (EVA), Fischer-Tropsch waxes, and mixtures of these materials.
- F.R.P. fully refined paraffin
- amorphous polymers and co-polymers such as, amorphous polypropylene, amorphous polyethylene, amorphous ethylene-vinyl acetate (EVA), Fischer-Tropsch waxes, and mixtures of these materials.
- the method of the present invention can be used to degrade any polymer which is non-thermosetting
- the bubble size of the oxygen-containing gas must be kept below about 10.0 mm and the flow rate of the gas must be kept above 2 c.f.m./1000 lbs. of reactant.
- a flow rate of this magnitude can be achieved using conventional apparatus for handling pressurized gases.
- the bubble size can be achieved by dispersing the pressurized gas through a metal mesh work, or more simply and preferably, by dispersing it from a slit cut along the length of an elongated tube which is placed along the bottom of the reaction vessel.
- reaction is preferably carried out at atmospheric pressure, special pressurized vessels and the like are not required. Rather, all that is required is a conventional heated reaction vessel having an inner surface which will not react with the polymer being depolymerized. Similarly, conventional stirring equipment can be used when it is desired to stir the molten polymer during the reaction. In running the reaction, it has been found preferable to place some previously depolymerized material in the reactor at the beginning of the reaction, i.e., to charge the reactor with a "heel" of previously depolymerized material.
- a preferred application of the invention involves the depolymerization of amorphous (non-crystalline) polypropylene.
- crystalline polypropylene is a thermoplastic material which can be prepared by polymerization of propylene with the aid of catalysts. This polymar is important commercially because of its good mechanical properties, workability, and relatively high melting point.
- Amorphous polypropylene is a by-product resulting from the production of crystalline polypropylene. Its physical properties, including viscosity and softening point, vary considerably from batch to batch, and, as produced, it generally has little or no commercial value. However, by reducing its viscosity and softening point, amorphous polypropylene can be made suitable for various industrial purposes, including being used as a filler (flooding material) for communication (telephone) cables and the like.
- conventional thermal oxidative degradation of amorphous polypropylene has involved the following five steps: (i) holding the starting material at approximately 430° F. until the softening point (Ring and Ball) is approximately 275° F. or below; (ii) cooling the reaction to approximately 375° F.; (iii) adding peroxide catalyst in 0.1% (w/w) increments until the viscosity at 347° F. is 250 centipoise (cps) or below and the softening point is approximately 267° F. or below; (iv) heating the reactants to approximately 400°-410° F. to deactivate the peroxide; and (v) adding 10% (w/w) amorphous polyethylene and 0.2% (w/w) oxidation inhibitor.
- the reaction time for this conventional process has been approximately 15-16 hours.
- the method of the present invention results in significant improvements over the conventional process. Specifically, it allows the oxidative decomposition of amorphous polypropylene to occur at a lower temperature, it eliminates the need for peroxide catalysts, and it decreases the overall reaction time to as much as one-eighth of the time required for the conventional depolymerization.
- thermal oxidative degradation of amorphous polypropylene is preferably performed by: (i) holding the starting material at approximately 385°-405° F., i.e., at a lower temperature than the conventional process; (ii) stirring the material at approximately 65-70 rpm using a LIGHTNIN mixer while sparging the molten reactant mixture with fine air bubbles having a diameter less than about 5 mm at a rate of approximately 4-8 c.f.m./1000 lbs. of reactor charge; (iii) stopping the sparging when the viscosity of the reactant mixture at 347° F. is approximately 250 cps and the softening point is approximately 267° F. or below; and (iv) adding 10% (w/w) amorphous polyethylene and 0.2% (w/w) of oxidation inhibitor.
- the total reaction time for this process is approximately 2 to 5 hours.
- the process of the present invention is simpler and more straightforward than the prior art process. Moreover, following the inventive procedure has been found to result in improved products compared to products produced by the conventional procedure. Specifically, because of the lower temperatures used and the shorter reaction time, the products of the present invention have a lighter color and less odor than prior art products.
- Amorphous polypropylene was depolymerized in accordance with conventional methodology as follows. One thousand (1000) grams of amorphous polypropylene was heated in a glass reactor for 5 hours at 430° F. The material was cooled to 375° F. and 0.4% (w/w) peroxide (benzoyl peroxide) was added in 0.1% increments. The material was then held at 375° F. for an additional 9 hours. The peroxide was then deactivated by raising the temperature of the reactor to approximately 400°-410° F. Ten percent (10%) amorphous polyethylene (w/w) and 0.2% (w/w) of an oxidation inhibitor (IRGANOX 1010) were then added. The viscosity (at 347° F.) and softening point (Ring and Ball) of the end product were then measured, and the color of the product was determined by visual examination.
- IRGANOX 1010 an oxidation inhibitor
- amorphous polypropylene 1000 grams were heated in a glass reactor for 4.5 hours at a constant temperature of 385° F. with continuous stirring at 65-70 r.p.m. using a standard laboratory stirrer. The material was continuously sparged with fine air bubbles (about 1 mm in diameter) at a rate of 0.5 liters per minute. At the end of the reaction period, 10% (w/w) amorphous polyethylene and 0.2% (w/w) oxidation inhibitor (IRGANOX 1010) were added. The viscosity (at 347° F.) and softening point (Ring and Ball) were then measured, and the color of the product was determined by visual examination.
- This example illustrates the use of the inventive process to depolymerize amorphous polypropylene having a high initial viscosity.
- the final product was very tacky and pliable, with a very light color. It had a viscosity at 347° F. of 302 cps and a softening point (Ring and Ball) of 277° F.
Abstract
Description
TABLE I ______________________________________ Results of experiments comparing conventional thermal oxidative degradation of amorphous polypropylene with the method of the invention Conventional Oxidation Invention Method Method ______________________________________ Viscosity (cps) Initial 500 460 Final 147 138 Max. Reaction Temp. (°F.) 430 385 Reaction Time (hrs) 14 4.5 Softening Point (°F.) Initial 304 306 Final 300 267 Peroxide Catalyst + - Air Sparging - + ______________________________________
Claims (10)
Priority Applications (1)
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US06/699,658 US4624993A (en) | 1985-02-08 | 1985-02-08 | Method for depolymerizing polymers |
Applications Claiming Priority (1)
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US06/699,658 US4624993A (en) | 1985-02-08 | 1985-02-08 | Method for depolymerizing polymers |
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US4624993A true US4624993A (en) | 1986-11-25 |
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US06/699,658 Expired - Fee Related US4624993A (en) | 1985-02-08 | 1985-02-08 | Method for depolymerizing polymers |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4766166A (en) * | 1987-02-13 | 1988-08-23 | Moore And Munger Marketing And Refining, Inc. | Compositions having the properties of low viscosity polyethylenes |
US5530073A (en) * | 1995-06-30 | 1996-06-25 | Amoco Corporation | Process for increased peroxide efficiency in controlled rheology polypropylene resin |
EP0799839A2 (en) * | 1996-04-02 | 1997-10-08 | Montell North America Inc. | Radiation visbroken polypropylene and fibers made therefrom |
US20150125693A1 (en) * | 2012-07-17 | 2015-05-07 | Henkel Ag & Co. Kgaa | Protective elements made of polyolefin hot-melt adhesives |
Citations (18)
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US2828296A (en) * | 1957-02-11 | 1958-03-25 | Eastman Kodak Co | Emulsifiable polypropylene wax and manufacture thereof |
US2911384A (en) * | 1957-02-05 | 1959-11-03 | Sun Oil Co | Oxygenated crystalline polypropylene, method of making, and wax composition containing same |
US2928797A (en) * | 1957-09-12 | 1960-03-15 | Eastman Kodak Co | Aqueous dispersion of synthetic polymers for floor polishing composition |
US3110708A (en) * | 1959-07-31 | 1963-11-12 | Basf Ag | Process for the thermal oxidative degradation and simultaneous purification of linear polyolefines |
US3130186A (en) * | 1960-08-09 | 1964-04-21 | Glanzstoff Ag | Process for the dissociation of polypropylene |
US3160621A (en) * | 1955-02-08 | 1964-12-08 | Eastman Kodak Co | Emulsifiable waxes from polyethylene |
US3177193A (en) * | 1960-07-15 | 1965-04-06 | Phillips Petroleum Co | Process of improving the moldability and extrudability of solid olefin polymers |
US3201381A (en) * | 1962-06-20 | 1965-08-17 | Eastman Kodak Co | Emulsifiable polyethylene waxes and process of preparation |
US3227703A (en) * | 1963-01-28 | 1966-01-04 | Eastman Kodak Co | Process for deodorizing thermally degraded, unoxidized polyolefins |
US3232917A (en) * | 1960-03-07 | 1966-02-01 | Eastman Kodak Co | Oxidation of crystalline poly-alpha-olefins |
US3383375A (en) * | 1962-05-18 | 1968-05-14 | Shell Oil Co | Treatment of polypropylene articles |
US3519588A (en) * | 1963-03-08 | 1970-07-07 | Eastman Kodak Co | Emulsifiable waxes from polyolefins |
US3563972A (en) * | 1969-10-15 | 1971-02-16 | Exxon Research Engineering Co | Low melt elasticity composition of polypropylene |
US3655834A (en) * | 1969-11-13 | 1972-04-11 | Basf Ag | Lowering the molecular weight of high molecular weight polyethylene in the powder phase |
US3700639A (en) * | 1971-12-22 | 1972-10-24 | Sinclair Koppers Co | Crystalline polystyrene products |
US3898209A (en) * | 1973-11-21 | 1975-08-05 | Exxon Research Engineering Co | Process for controlling rheology of C{HD 3{B {30 {0 polyolefins |
US4145526A (en) * | 1977-01-10 | 1979-03-20 | Solvay & Cie | Process for depolymerizing hydroxycarboxylic polymers |
US4145493A (en) * | 1977-12-01 | 1979-03-20 | Standard Oil Company (Indiana) | Oxidation of rubbery polymeric hydrocarbons |
-
1985
- 1985-02-08 US US06/699,658 patent/US4624993A/en not_active Expired - Fee Related
Patent Citations (18)
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US3160621A (en) * | 1955-02-08 | 1964-12-08 | Eastman Kodak Co | Emulsifiable waxes from polyethylene |
US2911384A (en) * | 1957-02-05 | 1959-11-03 | Sun Oil Co | Oxygenated crystalline polypropylene, method of making, and wax composition containing same |
US2828296A (en) * | 1957-02-11 | 1958-03-25 | Eastman Kodak Co | Emulsifiable polypropylene wax and manufacture thereof |
US2928797A (en) * | 1957-09-12 | 1960-03-15 | Eastman Kodak Co | Aqueous dispersion of synthetic polymers for floor polishing composition |
US3110708A (en) * | 1959-07-31 | 1963-11-12 | Basf Ag | Process for the thermal oxidative degradation and simultaneous purification of linear polyolefines |
US3232917A (en) * | 1960-03-07 | 1966-02-01 | Eastman Kodak Co | Oxidation of crystalline poly-alpha-olefins |
US3177193A (en) * | 1960-07-15 | 1965-04-06 | Phillips Petroleum Co | Process of improving the moldability and extrudability of solid olefin polymers |
US3130186A (en) * | 1960-08-09 | 1964-04-21 | Glanzstoff Ag | Process for the dissociation of polypropylene |
US3383375A (en) * | 1962-05-18 | 1968-05-14 | Shell Oil Co | Treatment of polypropylene articles |
US3201381A (en) * | 1962-06-20 | 1965-08-17 | Eastman Kodak Co | Emulsifiable polyethylene waxes and process of preparation |
US3227703A (en) * | 1963-01-28 | 1966-01-04 | Eastman Kodak Co | Process for deodorizing thermally degraded, unoxidized polyolefins |
US3519588A (en) * | 1963-03-08 | 1970-07-07 | Eastman Kodak Co | Emulsifiable waxes from polyolefins |
US3563972A (en) * | 1969-10-15 | 1971-02-16 | Exxon Research Engineering Co | Low melt elasticity composition of polypropylene |
US3655834A (en) * | 1969-11-13 | 1972-04-11 | Basf Ag | Lowering the molecular weight of high molecular weight polyethylene in the powder phase |
US3700639A (en) * | 1971-12-22 | 1972-10-24 | Sinclair Koppers Co | Crystalline polystyrene products |
US3898209A (en) * | 1973-11-21 | 1975-08-05 | Exxon Research Engineering Co | Process for controlling rheology of C{HD 3{B {30 {0 polyolefins |
US4145526A (en) * | 1977-01-10 | 1979-03-20 | Solvay & Cie | Process for depolymerizing hydroxycarboxylic polymers |
US4145493A (en) * | 1977-12-01 | 1979-03-20 | Standard Oil Company (Indiana) | Oxidation of rubbery polymeric hydrocarbons |
Non-Patent Citations (6)
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Asinger, F., Paraffins, Chemistry and Technology, 1968, pp. 583 604. * |
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Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4766166A (en) * | 1987-02-13 | 1988-08-23 | Moore And Munger Marketing And Refining, Inc. | Compositions having the properties of low viscosity polyethylenes |
US5530073A (en) * | 1995-06-30 | 1996-06-25 | Amoco Corporation | Process for increased peroxide efficiency in controlled rheology polypropylene resin |
EP0799839A2 (en) * | 1996-04-02 | 1997-10-08 | Montell North America Inc. | Radiation visbroken polypropylene and fibers made therefrom |
EP0799839A3 (en) * | 1996-04-02 | 1997-10-22 | Montell North America Inc | |
US5804304A (en) * | 1996-04-02 | 1998-09-08 | Montell North America Inc. | Radiation visbroken polypropylene and fibers made therefrom |
EP0980877A2 (en) * | 1996-04-02 | 2000-02-23 | Montell North America Inc. | Radiation visbroken polypropylene and fibers made therefrom |
EP0980877A3 (en) * | 1996-04-02 | 2001-01-17 | Montell North America Inc. | Radiation visbroken polypropylene and fibers made therefrom |
US20150125693A1 (en) * | 2012-07-17 | 2015-05-07 | Henkel Ag & Co. Kgaa | Protective elements made of polyolefin hot-melt adhesives |
US9725627B2 (en) * | 2012-07-17 | 2017-08-08 | Henkel Ag & Co. Kgaa | Protective elements made of polyolefin hot-melt adhesives |
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